1. Field of the Invention
The present invention relates to an occupant protection device, particularly to an occupant protection device in which an air bag body is housed in the center pad of a steering wheel.
2. Description of the Related Art
Conventionally, there has been known an occupant protection device in which an air bag body is folded and housed in the center pad of a steering wheel and is expanded toward the occupant upon the vehicle experiencing an impact so that the occupant is protected against the impact.
Here, the center pad of the steering wheel normally rotates along with the steering wheel in accordance with a driving operation of the occupant. For this reason, the air bag body housed in the center pad is formed so as to be circular so that the air bag body can be inflated and expanded with the same shape for any steering angle of the steering wheel. The air bag body formed in a circular shape mainly protects the head of the occupant.
In recent years, there has been an increasing need for an air bag body housed in a steering wheel, which is capable of protecting not only the head of the occupant, but also other body parts of the occupant sufficiently. Normally, the chest of the occupant is restrained by a seat belt.
Accordingly, a strong pressure may be applied to the chest upon the vehicle experiencing an impact, and thus there has been an increasing need for protecting the chest of the occupant sufficiently by reducing the pressure applied to the chest upon the impact.
As a device capable of protecting not only the head of the occupant but also other body parts of the occupant, for example, Japanese Unexamined Patent Application Publication (JP-A) No. 2006-069384 discloses an air bag device for an automobile, in which an air bag body is mounted on a center pad configured not to rotate, the air bag body being formed in such a manner as to include a head protection portion, a chest protection portion, and an abdomen protection portion.
In JP-A No. 2006-069384, the air bag body is housed in the center pad which is configured not to rotate, and thus the shape of the air bag can be decided upon in advance, and accordingly, the air bag body protects not only the head of the occupant but also the chest and abdomen of the occupant. However, for example, there is room for improvement regarding the way in which the waist and legs of the occupant are restrained.
Accordingly, with the air bag device in the JP-A No. 2006-069384, the knees of the occupant may be raised in the upward vertical direction of the vehicle upon the vehicle experiencing an impact. A phenomenon that the knees of the occupant are raised in this manner upon the vehicle experiencing an impact is what is called a submarine phenomenon. With the air bag device in the JP-A No. 2006-069384, the submarine phenomenon may cause the chest of the occupant to be compressed.
As described above, the air bag body in the JP-A No. 2006-069384 is expanded between the steering wheel and the chest of the occupant so as to protect the chest of the occupant. The air bag body, however, is not inflated and expanded between the legs of the occupant and the lower edge of the steering wheel in the vertical direction of the vehicle.
Here, for example, in a vehicle such as a full cab or semi cab vehicle, the steering wheel may move toward the front side of the vehicle along with the steering shaft upon the vehicle experiencing an impact. Accordingly, in a vehicle such as a full cab or semi cab vehicle, the chest of the occupant may be urged and pressed against the lower edge of the steering wheel upon the vehicle experiencing an impact.
As described above, the air bag device in the JP-A No. 2006-069384 protects the head as well as the chest and abdomen of the occupant, however, the air bag body is not inflated and expanded so as to cover the lower edge of the steering wheel in the vertical direction of the vehicle, and thus there is room for improvement in reducing the pressure applied to the chest and improving the safety of the occupant.